Early prevention of frost damage to wheat hinges on applying adequate freeze‑protection irrigation.

Before we know it, it’s already late November, and the weather is growing colder. How can wheat safely survive the winter? Many farmers are aware that irrigating wheat can help protect it from frost—so how can you apply this frost‑protection watering most effectively? Let’s take a look!

Benefits of Applying Freeze‑Protection Irrigation to Wheat

First, ensuring an adequate supply of soil moisture during the winter period is conducive to consolidating pre-winter tillering and promoting the development of new tillers.

Second, it serves to store winter moisture for spring use, helping to maintain favorable soil moisture conditions in early spring after the New Year, delaying the first spring fertilization and irrigation, and enabling more proactive management while promoting robust seedling development.

Third, it accelerates the decomposition of crop residues. Currently, most wheat fields employ the direct‑return‑of‑corn‑straw‑to‑the‑field technique. During decomposition, straw requires a certain amount of moisture; adequate moisture promotes its breakdown. At the same time, this process stimulates microbial activity and speeds up the decomposition and transformation of fertilizer nutrients, thereby providing more nutrients to support wheat growth and development after the winter.

Fourth, enhancing the soil’s thermal conductivity can effectively reduce diurnal temperature fluctuations in the field and prevent frost damage that leads to seedling death caused by rapid temperature swings.

Fifth, it can compact the soil, promote freeze–thaw weathering of clods, fill cracks, and eliminate overwintering pests, thereby facilitating tillering around the base of the plant.

Sixth, it helps suppress soil salinity and protect seedlings, while also mitigating the onset of soil salinization.

The timing for applying freeze‑protection irrigation to wheat

The key to applying freeze‑protection irrigation to wheat is timing—adjusting according to the weather, soil conditions, and crop vigor.

1. Monitor air temperature: Winter irrigation is best carried out when the daily average temperature has stabilized around 3°C. If done too early, higher temperatures and vigorous evaporation will prevent water from being retained to improve soil moisture, and excessive water and fertilizer may lead to overly vigorous seedling growth—potentially even premature stem elongation before winter—resulting in severe frost damage. If delayed too long, lower temperatures hinder water infiltration, causing surface water to accumulate and form an ice crust.

2. Assess soil moisture: In the 5–20 cm soil layer, if sand soils have a water content below 13%, loam soils below 15%, or clay soils below 17%, or if the soil’s relative humidity falls below 60%, winter irrigation is required. If these thresholds are exceeded, irrigate sparingly or refrain from irrigation altogether. For wheat grown on rice stubble, where the lower soil layer is adequately moist but soil temperature remains low, avoid excessive flood irrigation to prevent seedlings from turning reddish or yellowing, or even dying. Instead, adopt methods such as sprinkler irrigation, pit‑irrigation, or surface application to help raise soil temperature and protect the seedlings.

3. Assessing crop conditions: For early‑sown wheat with vigorous seedlings, soil moisture is typically adequate, so irrigation can be delayed or omitted. In contrast, flood‑damaged fields and late‑sown wheat, which are sown later and have a shorter pre‑winter growth period with insufficient accumulated heat units, often produce single tillers or weak stands. To make the most of the limited effective heat units available during the brief warm spells in early winter and to promote tillering and root development, it is generally preferable not to irrigate—except on excessively dry plots—but an early “green-up” irrigation may be applied as needed.

Precautions for Applying Winter Irrigation to Wheat

1. For winter irrigation, apply enough water to thoroughly saturate the soil, ensuring that the water has fully infiltrated by the end of the day. Avoid flood‑irrigation.

2. It is best to water between 9 a.m. and 3 p.m. on clear, warm days.

3. Combine irrigation with topdressing. For wheat fields with insufficient base fertilizer, weak seedlings, and a small stand, apply 5 kg of Yidan per 2–3 mu during the winter‑to‑spring irrigation, using the winter fertilizer in spring to promote the transformation and growth of the wheat seedlings.

4. After applying freeze‑thaw irrigation, promptly hoe and rake the wheat. Once the field is walkable, carry out timely hoeing and raking to break up soil compaction, prevent surface cracking, and control weeds while conserving soil moisture. This promotes vigorous seedling growth aboveground and robust root development belowground.